An Organic Light-Emitting Diode (OLED) display is a hot spot in a research field of flat-panel displays at present, and has advantages of low energy consumption, low production cost, self-illumination, wide viewing angle, fast response speed and the like as compared with a Liquid Crystal Display (LCD). At present, OLED has begun to replace a traditional LCD screen in display fields of cellphones, Personal Digital Assistants (PDAs), digital cameras and the like.
Different from the LCD in that brightness is controlled with a stable voltage, the OLED is driven by current, and needs stable current to control light-emitting. Due to a technological process, device aging and so on, a threshold voltage Vth of a driving transistor of a pixel circuit has non-uniformity, which results in that the current flowing through each pixel point OLED changes such that the display brightness is non-uniform, thus affecting a display effect of a whole image.
A pixel circuit which can be shared for both internal compensation and external compensation is required.